Rather than storing a mangled name in a Swift protocol descriptor,
which encodes information that is redundant with the context of the
protocol, store an unmangled name as in nominal type descriptors. Update
the various places where this name is used to extract the demangle
tree from the context descriptors.
Reimplement protocol descriptors for Swift protocols as a kind of
context descriptor, dropping the Objective-C protocol compatibility
layout. The new protocol descriptors have several advantages over the
current implementation:
* They drop all of the unused fields required for layout-compatibility
with Objective-C protocols.
* They encode the full requirement signature of the protocol. This
maintains more information about the protocol itself, including
(e.g.) correctly encoding superclass requirements.
* They fit within the general scheme of context descriptors, rather than
being their own thing, which allows us to share more code with
nominal type descriptors.
* They only use relative pointers, so they’re smaller and can be placed
in read-only memory
Implements rdar://problem/38815359.
This adds the dllstorage annotations on the tests. This first pass gets
most of the IRGen tests passing on Windows (though has dependencies on
other changes). However, this allows for the changes to be merged more
easily as we cannot regress other platforms here.
The size of a protocol's metadata was not a multiple of 8 bytes, so
on 64-bit platforms, the runtime would copy default witnesses from
the wrong address, because IRGen metadata does not add alignment padding,
whereas the in-memory structure does.
Fix this by adding a 32-bit padding field at the end of the protocol
descriptor. Technically this is not necessary on 32-bit, but this keeps
things simpler for now.
The test case for this is a library evolution test exercising resilient
default protocol requirements, but it is not quite ready to go in yet.
This prevents the linker from trying to emit relative relocations to locally-defined public symbols into dynamic libraries, which gives ld.so heartache.
IRGen now uses a ConstantBuilder to build protocol metadata, which may
now have additional fields at the end for default witnesses.
For now, the default implementations in the test have to external
because IRGen cannot emit a witness_method body where Self is
abstract. I will fix this by passing in the witness table as part
of the witness_method calling convention.
On the IRGen side, other than the calling convention change, the only
remaining piece here is emitting GenericWitnessTables and accessor
functions for conformances where the conformance is defined in
a different module than the protocol, and the protocol is resilient.
Sema still needs to infer default witnesses and store them in the
ProtocolDecl, so that SILGen can emit default witness thunks for
them.
'Ss' appears in manglings tens of thousands of times in the standard library and is also incredibly frequent in other modules. This alone is enough to shrink the standard library by 59KB.
Swift SVN r32409
@objc protocols aren't supported with an ObjC runtime, but we still want values of AnyObject type to be word-sized. Handle this by turning the binary "needsWitnessTable" condition into a "dispatch strategy" enum, so we can recognize the condition "has no methods, so neither swift nor objc dispatch" as distinct from either swift or ObjC protocol representations. Assign this dispatch strategy when we lower AnyObject. Should be NFC for the ObjC-enabled build.
(It would also be beneficial for the ObjC-runtime-enabled version of Swift if AnyObject weren't an @objc protocol; that would mean we could give it a canonical protocol descriptor in the standard library, among other things. There are fairly deep assumptions in Sema that AnyObject is @objc, though, and it's not worth disturbing those assumptions right now.)
Reapplying with updates to the runtime unit tests.
Swift SVN r27341
@objc protocols aren't supported with an ObjC runtime, but we still want values of AnyObject type to be word-sized. Handle this by turning the binary "needsWitnessTable" condition into a "dispatch strategy" enum, so we can recognize the condition "has no methods, so neither swift nor objc dispatch" as distinct from either swift or ObjC protocol representations. Assign this dispatch strategy when we lower AnyObject. Should be NFC for the ObjC-enabled build.
(It would also be beneficial for the ObjC-runtime-enabled version of Swift if AnyObject weren't an @objc protocol; that would mean we could give it a canonical protocol descriptor in the standard library, among other things. There are fairly deep assumptions in Sema that AnyObject is @objc, though, and it's not worth disturbing those assumptions right now.)
Swift SVN r27338
